1. Field of the Invention
The invention relates generally to low air loss support systems and more particularly to a low air loss mattress which can be used on hospital beds.
2. Discussion of Related Art
In recent years, low air loss beds have come into extensive use and are used widely in hospitals to prevent and treat decubitus ulcers which are commonly referred to as bed sores. A primary cause of bed sores is the inability of the patient to move so as to relieve pressure points. These pressure points typically occur in the area of a bony protuberance which results in a cut-off of the blood flow in the skin and soft tissue adjacent to the protuberance when distortion of capillary beds curtails blood flow. When the blood flow in the capillaries is blocked due to excessive external (interface) pressure, the cells in that area begin to die and may result in a wound which is called a bed sore. Mobile persons do not have this problem because they continually move even when asleep which eliminates the cut-off of blood flow for too long a period.
A typical low air loss support system has a plurality of parallel gas or vapor-permeable cells inflated to provide support for the patient. The low air loss support systems provide gradual leakage of air from the cells, either by having holes at selected locations or by providing a cell material which is permeable to air. Usually, air is pumped from a manifold on one side of the bed through the cells extending transversely of the bed. The air is wholly or partially exhausted through the holes or pores in the cells. The air losses necessitate the use of a rather large air pump, and the systems constructed of this type tend to be bulky and expensive.
Ideally, each inflatable cell should have a sufficient height to allow a substantial amount of depression of each cell for supporting the patient over a larger surface area and the pressure within the inflated cell should be as low as possible to maximize the pressure-reducing effect. However it is important that no part of the mattress is depressed to such an extent by the patient lying thereon that the patient makes contact with any underlying support surface. Such a problem is frequently encountered when a patient is in the sitting position on the bed or in the event of a power failure when the cells continue deflating through air loss through the holes but the pump is no longer inflating the cells. A similar problem may occur during transport of a patient when the cells may have to be disconnected from the pump for a period of time.